System and method for biologically treating wastewater using low density, high surface area substrates

ABSTRACT

A treatment system of the present invention generally includes a plurality of high surface area sheets anchored to a fixed base. The sheets are generally vertically oriented although able to flex and sway independently. Substantially all regions of substantially all sheets are aerated. The sheets are constructed of an open weave substrate that allows the diffusion of gas, nutrients and food, while protecting and serving as an attachment site for a variety of microbial colonies in both anoxic and aerobic zones. In use a system of the present invention is inserted into a wastewater reservoir, and aerated, for treatment of the wastewater.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation in Part of U.S. patent applicationSer. No. 16/147,144 filed Sep. 28, 2018, which claims the benefit ofprovisional patent application Ser. No. 62/565,800, filed Sep. 29, 2017.Related applications are entitled SYSTEM AND METHOD FOR BIOLOGICALLYTREATING WASTEWATER USING LOW DENSITY, HIGH SURFACE AREA SUBSTRATES. Thenon-provisional and provisional applications are hereby incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to a system and method for biologically treatingwater, and in particular to a treatment system and method having aplurality of vertically positioned low density, high surface areasubstrate sheets attached to a fixed base.

Description of the Prior Art

Proper remediation of wastewater is critical to life, health and theenvironment. Many major advancements in human civilization andcatastrophic historical events can be linked to the presence or absenceof clean drinking water, and/or the presence or absence of contaminatedwater.

Wastewater treatment is the physical, chemical, and/or biologicalprocesses of removing contaminants from wastewater in order to producewater that is environmentally safer. Safe drinking water from amunicipal water source is an example of treated wastewater.

Wastewater treatment has two major components: primary treatment removescontaminants including grease, dirt, gravel, and floatable waste; andsecondary treatment removes additional suspended solids and pollutants.Secondary treatment often incorporates biological processes.

Known attached growth biological processes include moving bedbioreactors (MBBR), submerged fixed film (SFF), integrated fixed-filmactivated sludge (IFAS), and trickling filters or biofilters. Wastewateris intermittently or continuously flowed over or through the media.Microorganisms become attached to the media and form a biological layeror fixed film. Organic matter in the wastewater diffuses into the film,where it is metabolized. As organisms grow and reproduce, the biofilmthickness increases, with portions of the film periodically sloughingoff.

In what are considered improvements on the aforementioned attachedgrowth biological process technologies, a variety of growth mediasystems for treating wastewater, and module-based systems for treatingwastewater, have evolved. The Applicant's patents listed herein areincorporated by reference in their entirety: System for treatingwastewater and a controlled reaction-volume module usable therein, U.S.Pat. No. 7,445,715 B2, filed Nov. 22, 2005; Wastewater treatment method,U.S. Pat. No. 7,854,843 B2, filed Mar. 8, 2010; System for treatingwastewater having a controlled reaction-volume module usable therein,U.S. Pat. No. 7,691,262 B2, filed Oct. 13, 2008; Media for supportinggrowth biology within a wastewater treating system, U.S. Pat. No.D718412 S1, filed Dec. 3, 2012; Extruded media for supporting growthbiology within a wastewater treating system, U.S. Pat. No. D618760 S1,filed Nov. 2, 2009; Media for supporting growth biology within awastewater treatment system, U.S. Pat. No. D762279 S1, filed Nov. 24,2014; Anoxic system screen scour, U.S. Pat. No. 8,568,593 B1, filed Jun.2, 2010; and Extruded media for supporting growth biology within awastewater treating system, U.S. Pat. No. D672009 S1, filed Jun. 8,2010.

Of particular relevance are modular wastewater treatment systems whichemploy a plurality of substrate sheets positioned in parallel, typicallywithin a framework that secures each substrate sheet around theperimeter of the sheet, and an integrated aeration system. In use amodular wastewater treatment system is introduced into an opened orclosed wastewater repository, such as a treatment lagoon or tank, andthe substrate sheets are eventually colonized by microbes that remediatethe contamination. Known modular wastewater treatment systems, however,have some shortcomings.

One negative aspect of known modular wastewater treatment systems isthat each individual substrate sheet, usually four-sided, requiressupport on multiple sides in order to prevent the sheet from crumplingand sinking. This “framework” adds to the weight, cost, materials, andlikelihood of failure of the system.

Another disadvantage of the framework is that each individual substratesheet is substantially stationary. This means that biomass sloughs offat a slow rate—typically when the mass is too great to be supported bythe substrate.

Another disadvantage of the framework is that the removal of one sheet,for example due to damage, is difficult since the adjacent sheets cannoteasily be moved aside to make space for removal of the damaged sheet.

Another negative aspect of known wastewater treatment systems is thatthe substrates are less than ideal. More specifically, substrates tendto be fairly planar in overall shape, thereby providing littleprotection for emerging microbial colonies.

Another disadvantage of known fairly planar substrates is that theyprovide a habitat for a limited number of microbial species, therebylimiting the variety of wastes that can be consumed within the biofilm.

Another disadvantage of known fairly planar substrates is that theydon't provide a steep and sustained gradient of oxygen concentration. Anoxygen gradient is required to allow development of both aerobic andanoxic zones, thereby simultaneously facilitating nitrification anddenitrification.

As can be seen, there is a need for a wastewater treatment system thatdoesn't require a framework for substrate sheets. It is desirable thatthe system facilitates shedding excess biomass. It is also desirablethat substrate sheets in the system can be replaced fairly quickly andeasily. It is also desirable that the system includes a substrate thatphysically protects emerging microbial colonies, provides a habitat to awide variety of microbial species, and lends itself to providing a steepand sustained oxygen concentration gradient.

SUMMARY OF THE INVENTIONS

A treatment system of the present invention generally includes aplurality of sheets anchored along at least one edge to at least onefixed base. The sheets are preferably flexible and constructed of a highsurface area substrate.

At least one aerator releases air to the sheets via a plurality ofspaced apart diffusers, thereby aerating substantially all regions ofsubstantially all sheets.

The density of the sheets can provide buoyancy in wastewater so thesheets are generally vertical, but able to flex and sway independently.This movement facilitates sloughing off of biomass, and the removal andreplacement of individual sheets as desired.

The open weave structure of the substrate allows gas, nutrients and foodto diffuse, yet provides protection and attachment sites for emergingmicrobial colonies. Also, both anoxic and aerobic zones emerge, therebyallowing simultaneous nitrification and denitrification within the samesystem. The system supports a variety of growth including AOB, NOB, PAOand annamox microorganisms

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of the present invention with sheets attachedalong the bottom edges;

FIG. 2 is a depiction of the present invention with sheets attachedalong side edges;

FIG. 3 is a depiction of the present invention with sheets attachedalong the top edges;

FIG. 4 is a depiction of the present invention in use;

FIG. 5 depicts a side view of freely flexing and swaying sheets;

FIG. 6 is a top-view close-up depiction of the substrate;

FIG. 7 is a perspective side-view close-up depiction of the substrate;

FIG. 8 depicts the oxygen gradient in the substrate;

FIG. 9 depicts an embodiment with a sheet connected to tank; and

FIG. 10 depicts and embodiment employing a frame.

DETAILED DESCRIPTION AND THE PREFERRED EMBODIMENTS

The following detailed description is of the best currently contemplatedmodes of carrying out exemplary embodiments of the invention. Thedescription is not to be taken in a limiting sense but is made merelyfor the purpose of illustrating the general principles of the invention,since the scope of the invention is best defined by the appended claims.

Treatment system 10 generally includes a plurality of sheets 20 anchoredto fixed base 30 in a substantially vertical orientation. Sheets may beanchored in parallel, or at an offset angle to each other, or acombination of both, and may be positioned substantially equidistantapart. As used herein, a “base” is a structure for anchoring sheets andmay be positioned on the floor, walls, upper edge or cover of a tank.“Fixed base” 30 is so named because it is substantially stable andwithout intentionally movable parts, however it should be understoodthat the fixed base is portable as a unit, for example from onewastewater repository to another.

FIGS. 1-3 depict three different embodiments: sheets 20 attached tofixed base 30 at bottom edge 33, at side edge 35, and at top edge 34,respectively. It should understood that various combinations ofattachment sites are within the scope of this invention. For example,sheets may be anchored on two edges, for example two side edges can beanchored on opposing tank walls, on the top and bottom of the tank, oron a wall and either the top or bottom of the tank. Sheets may also beanchored on three edges, for example from the bottom of the tank, or thetop of the tank, and two tank walls. Sheets may also be anchored on fouredges, for example from the top, bottom and opposing sides of the tank.

As shown in FIG. 4, treatment system 10 preferably includes fixed base30 for attaching sheets 20 thereto. In this embodiment each sheet 20 isanchored to fixed base 30 only along bottom edge 33. Attachment may beachieved by securing attachment site 26 of sheet, for example a grommet,to fixed base 30, by connection means 28, for example a zip-tie orsegment of steel wire or cable.

Treatment system 10 preferably includes aerator 40 that releases air tosheets 20 via diffusers 42. A plurality of spaced apart diffusers ispreferred, so as to enable aeration of substantially all regions ofsubstantially all sheets. However, aerators and diffusers are preferablyadjustable with respect to rate of discharge, and specific diffusers inuse, thereby allowing some variability as to regions which receive air,and amount of air received. Aerator 40 and/or air diffuser 42 may beattached to or integrated with fixed base 30, especially where bottomedge 33 is anchored. Alternatively, aerator 40 and/or air diffuser 42may be wholly separate structures from fixed base 30. As used herein,“air” shall refer to gaseous fluid including but not limited to ambientair, oxygen, nitrogen, and combinations thereof.

Regardless of the orientation of the sheet anchoring and fixed base, forexample bottom, walls, upper edge or cover, it is preferable to positionair diffuser 42 under sheets 20 so that bubbles of air 44 travelingupwardly travel along and through sheet 20.

As shown in FIGS. 4 and 5, sheets 20 may maintain a substantiallyvertical orientation without the assistance of stabilizing framework,attachment means at top edge 34 and/or side edges 35 of sheet, or thelike. This can be achieved by employing substrate 21 with a low(approximately 0.88 to approximately 0.98) specific gravity. In thisembodiment sheets are buoyant in wastewater and generally maintainvertical orientation when simply anchored at bottom edge. Thisconfiguration advantageously allows each sheet to flex and sway, forexample due to aeration and current forces, independently of othersheets. This orientation also allows sheets to be easily accessed andreplaced as needed, for example due to degradation or mechanical damage,by “pushing aside” surrounding sheets and detaching and adding sheet(s)as desired.

FIG. 5 shows in better detail how sheets 20 are substantially freelyflexing and swaying. These movements advantageously facilitate sloughingoff of excess biomass. Sheets are preferably positioned apartone-from-another such that each sheet is close enough to come in contactwith immediately surrounding sheet(s). This also facilitates sloughingoff of excess biomass via sheets “brushing up” against one another.

FIGS. 6 and 7 are close-up depictions of substrate 21 that forms sheets20. Substrate 21 generally includes two outer surfaces 22, with aplurality of fibers 24 joining the two surfaces. In a preferredembodiment each outer surface is approximately less than 3 mm thick, andthe total thickness of the substrate is approximately 3 mm toapproximately 20 mm. Outer surfaces preferably have a diamond shapedweave pattern, with the length of the sides of the diamonds beingbetween approximately 5 mm and approximately 20 mm. It should beunderstood that other weave patterns, for example circles, squares,triangles, hexagons, and so forth, are also within the scope of thisinvention. This open weave pattern allows gas, nutrient and food todiffuse to the biofilm surfaces at a high rate, which facilitates a highrate of wastewater treatment. It also provides “walls” that physicallyprotect and shield emerging microbial colonies when they are vulnerable.Fibers 24 provide a large amount of surface area per unit of volume offabric, and provide an ideal environment for microbial attachment andgrowth. Among the types of microbial growth may include AOB, NOB, PAOand annamox microorganisms

In a preferred embodiment the substrate has a surface area betweenapproximately 800 and approximately 4,000 square meters per cubic meter,and most preferably between approximately 1,000 and approximately 1,500square meters per cubic meter. In a preferred embodiment the substrateis constructed of polypropylene, but other plastics such as low densitypolyethylene or other fibers with a specific gravity of less thanapproximately 0.94 are also suitable. Apex Mills of Inwood, N.Y. is asource for custom designed 3-D spacer fabric that would be suitable foruse in this invention. In one embodiment the specific gravity of thesubstrate is approximately 0.88 to 0.98, with 0.91 to 0.96 beingparticularly desirable. The preferred polypropylene material has aspecific gravity of 0.91.

In an alternative embodiment a high density substrate is employed. Asused herein “high density” refers to a specific gravity betweenapproximately 1.0 and approximately 1.2. In this embodiment sheets 20are preferably attached to fixed base 30 positioned on upper portion oftank, for example upper walls, upper edges or on cover, with sheetshanging downwardly. Sheets may include weights (not shown) along bottomedge 33 to minimize swaying.

The structural characteristics of substrate 21, namely surfaces 22 thatallow gas, nutrients and food diffusion in combination withinterconnecting fibers 24 that create “deep recesses”, allow for thedevelopment of a steep and sustained gradient of oxygen concentration todevelop within the substrate. Referring to FIG. 8 which depicts one“diamond” of substrate 21, areas surrounded by substrate material, forexample where edges of diamonds meet, create anoxic zones 56, whileareas more central to center of diamond create aerobic zones 54. In theproper operating conditions these microhabitats support life for bothaerobic and anaerobic microbes, thereby supporting simultaneousnitrification and denitrification. It is noted that these metabolicactivities essentially mimic the desirable action of anammox bacteria,but without the challenges associated with maintaining viable anammoxcolonies.

FIG. 9 depicts an alternative embodiment of the present invention havingsheet 20 connected to walls 70 and floor 74, and along crossbeam 32 thatspans the top of the tank. Sheets are connected using connection means28. While the figure depicts attachment of sheet 20 along all fouredges, it should be understood that sheet can be attached along twoedges, for example from two opposing wall or from the top (crossbeam 32)and bottom (floor 74); or along three edges, preferably the floor andopposing walls.

Yet another alternative embodiment is depicted in FIG. 10 with sheets 20stabilized within frame 77. This embodiment preferably includes fixedbase 30 with aerator 40 and/or air diffuser 42 (not shown) between fixedbase and sheets, although not necessarily attached. In this embodimentthe entire module, including frame with sheets, fixed base and diffuser,is lowered into tank with fixed base resting on floor 74.

In use, a system of the present invention is inserted into a wastewaterreservoir in need of treatment. The aerator intake is positioned toensure it is above the surface of the wastewater, or otherwise doesn'tsuck in wastewater, and aerator parameters such as flow rate areadjusted according to the needs of the specific project. Air diffuser 42is preferably positioned below sheets so that rising bubbles travelupwardly along and through the surface of the substrate. The system isallowed to run, which leads to colonization of substrate by variousmicrobes, and treatment of wastewater by those microbes. The system ispreferably periodically examined to ensure integrity of sheets, properfunctioning of aerators and diffusers, and so forth. The system can beremoved for inspection by lifting the entire assembly from thewastewater. Because the system relies on only a fixed base, and not acomplete framework, the system is relatively light and easily removed.

Specifications of certain structures and components of the presentinvention have been established in the process of developing andperfecting prototypes and working models. These specifications are setforth for purposes of describing an embodiment, and setting forth thebest mode, but should not be construed as teaching the only possibleembodiment. Rather, modifications may be made without departing from thespirit and scope of the invention as set forth in the following claims.It should be understood that all specifications, unless otherwise statedor contrary to common sense, are +/−10%, and that ranges of values setforth inherently include those values, as well as all incrementsbetween. Moreover, “substantially” and the like shall mean generallytrue. By way of example, a substantially permanent attachment is capableof removal, but damage is likely to occur. A substantially planarsurface may have irregularities.

What is claimed is:
 1. A wastewater treatment device comprising: A. Aplurality of sheets with bottom edges positioned in parallel, each ofsaid sheets constructed of a substrate having two outer surfacesconnected with a multitude of fibers and a surface area of approximately1,200 to approximately 1,500 square meters per cubic meter; and B. Afixed base anchoring said bottom edges only.
 2. The wastewater treatmentsystem of claim 1 wherein said substrate has a specific gravity between0.88 and 0.98.
 3. The wastewater treatment system of claim 2 whereinsaid outer surfaces define a hexagonal surface pattern.
 4. Thewastewater treatment system of claim 2 wherein said outer surfacesdefine a diamond surface pattern.
 5. The wastewater treatment system ofclaim 4 wherein the length of sides of said diamond surface pattern isapproximately 5 mm to approximately 20 mm.
 6. The wastewater treatmentsystem of claim 2 wherein each of said substrates are constructed of amaterial selected from polypropylene, polyethylene, and combinationsthereof.
 7. A wastewater treatment system comprising: A. A plurality ofsubstantially freely flexing and swaying sheets, said sheets constructedof a woven substrate having two outer surfaces connected with amultitude of fibers; B. A base anchoring said sheets; C. An aeratoraligned below said sheets; D. Colonies of aerobic bacteria embedded insaid sheets; and E. Colonies of anaerobic bacteria embedded in saidsheets.
 8. The wastewater treatment system of claim 7 wherein saidsheets define at least one bottom edge movably anchored to said base. 9.The wastewater treatment system of claim 7 wherein said sheets define atleast one side edge movably anchored to said base.
 10. The wastewatertreatment system of claim 7 wherein said sheets define at least one topedge movably anchored to said base.
 11. The wastewater treatment systemof claim 7 wherein each of said plurality of sheets is positioned closeenough to contact immediately adjacent sheet or sheets.
 12. Thewastewater treatment system of claim 7 wherein said colonies of aerobicbacteria and anaerobic bacteria are embedded in said multitude offibers.
 13. The wastewater treatment system of claim 7 wherein saidsheets are a habitat for organisms selected from the group consisting ofplants, molds, fungi, viruses, protozoa, anammox bacteria, andcombinations thereof.
 14. A method of treating wastewater including theact of: A. Anchoring a plurality of substantially freely flexing andswaying sheets to a fixed base, each of said sheets constructed of awoven substrate having two outer surfaces connected with a multitude offibers and a specific gravity between 0.88 and 0.98; B. Introducing saidbase into a repository of wastewater; C. Aerating said sheets; and D.Allowing said sheets to colonize with microbes.
 15. The method of claim14 wherein said act of anchoring a plurality sheets consists of the actof anchoring said sheets along the bottom edge.
 16. The method of claim14 wherein said act of anchoring a plurality of sheets further includinganchoring a plurality of sheets wherein said substrate has a specificgravity greater than 1.00.